The invention relates to a thread-cutting device according to the preamble to patent claim 1.
In the case of a known thread-cutting device of this type (DE 44 28 049 A1), several toothed rods that exhibit, in each case, a radially inwardly-oriented oblique toothing, that is distributed across its circumference, are attached to a propulsion ring that is guided in such a way that it may be shifted axially. The spiral gearing meshes with a corresponding spiral gearing of transfer elements, which, in each case, simultaneously activate two tool slides in opposite directions. The propulsion, by way of a propulsion ring that is guided in such a way that it may be shifted axially has, on the one hand, the disadvantage that the toothed rods exhibit a relatively great distance from the axis of rotation. This generates a great structural volume of the thread-cutting head. On the other hand, the attachment of the toothed rod to a flange-like ring, which is attached only at the front, leads to the situation that the drive for the tool slide possesses a rigidity that is not, in all cases, sufficient. This can lead to imprecision in the processing of the work-piece.
In the case of another known solution (U.S. Pat. No. 2,093,506), too, propulsion is provided by means of an element in the form of a sleeve that is turned by means of a hollow shaft, whose central axis coincides with the axis of rotation, and which may be shifted in the axial direction by means of a hand lever that engages from the outside. When the axial shift occurs, the tool slides are advanced in a radial direction toward the axis of rotation.
In the case of this known solution, too, it is not possible to effect the motion of advancement by means of a central propulsion element.
Taking this state of the art as a point of departure, it is the underlying task of the invention to create a thread-cutting device that is constructed in a compact manner, which achieves, in the case of high production output, a high degree of processing precision, in which the advancement of the tool slides is possible by means of a centrally provided propulsion element.
The resolution of this task is accomplished with the characteristics of patent claim 1.
The embodiment according to the invention renders possible a compact and very rigid mode of construction of the thread-cutting device so that the radial, controlled repositioning of the tools can be accomplished very precisely, and its guiding can be accomplished in a manner involving a particularly low degree of oscillation. The embodiment according to the invention renders it possible to use thread-cutting tools and turning or rough-turning tools, as well as combined tools made of hard metal on each processed work-piece.
In the case of a particularly preferred embodiment form, the transfer of the axial motion of the propulsion element is accomplished directly onto the tool slide that is guided in a radially movable manner. By these means, the number of the parts, and thus, the amount of treasure and energy expended is less, when compared with the state of the art while, simultaneously, an enhanced degree of precision is produced.
Additional preferred embodiments of the invention result from the subsidiary claims.